Sodium carbonate and sodium bicarbonate solutions
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Commercial sodium carbonate is dissolved, and then it absorbs sulfur from the gas; as a result, the solution contains both sodium carbonate and sodium bicarbonate. However, the testing methods and procedures specified in the national standards are the same. I would like to ask whether hydrochloric acid titration is used in accordance with these national standards. The method using a mixed indicator to determine coloration shows whether it is sodium carbonate or sodium bicarbonate that is present; how can I calculate each separately after titration?
If sodium carbonate and sodium bicarbonate are mixed, a stepwise titration is required; that is, phenolphthalein is used at the first endpoint to titrate the conversion of sodium carbonate to sodium bicarbonate； Then, using methyl orange as an indicator, titrate the original sodium bicarbonate and the sodium bicarbonate formed from sodium carbonate. Calculating step by step yields the respective results.
Teacher, I couldn’t find any relevant standards; we still use the method of teaching by word of mouth. Could you provide a document containing the formulas as well? I am extremely grateful. Thank you, teacher